This invention generally relates to macroscopes; and more specifically, to a low magnification, high resolution and bright image macroscope that is simple to assemble.
Macroscopes are used to provide enlarged views of objects or specimens that are visible to the unaided eye. For instance, these instruments may be used to provide magnified views of whole groups of cells or small insects. In one type of application, for example, a small insect or a cluster of cells may be stained with a fluorescent dye and then illuminated with light while under observation in a macroscope. The macroscope enables a viewer to observe and to study how the cluster of cells react as a whole and how cells interact with each other.
Microscopes are not particularly well suited for low magnification, high resolution observations. This is so for a number of reasons. First, there are physical limitations on the size of a specimen that can be viewed and on the intensity with which a specimen can be illuminated using conventional microscopes. More specifically, conventional microscopes have more than two separate objective lens units on a rotating turret nosepiece that is mounted on the microscope frame. The objective lenses provide different magnification levels; and, for example, these objective lenses may magnify images by factors of ten, twenty, forty and one hundred respectively.
In use, the nosepiece is rotated to select the objective lens that is used to observe the specimen. In order to accommodate these objective lens units on a single nosepiece, conventionally, each objective lens is attached to the nosepiece via a mechanical thread of diameter 22.3 mm. This thread size places a physical limitation on the exit pupil diameter of the objective lens.
This size limitation affects the amount of light that can be transmitted or observed through the objective lens. To elaborate, the amount of light transmitted through a lens is proportional to the square of the diameter of the lens. Thus, if the diameter of a lens is doubled, the lens is able to transmit four times the light. Analogously, however, if the diameter of a lens is halved, the lens is able to transmit only one-fourth the light.
Spatial resolution of detail in a image that can be achieved with a lens is a function of the amount of light transmitted through the lens. The physical limitation due to thread size on the amount of light that can be transmitted through a microscope objective lens also acts to limit the spatial resolution that can be obtained with the lens.
This limitation particularly affects the light intensity that can be obtained with transmittance microscopes, where the specimen is illuminated with light from below the specimen. With these microscopes, the light passes through the specimen and on to the objective lens which forms an image of the specimen. Thus, the intensity with which the specimen is observed varies as a function of the second power of the diameter of the lens. The relationship is the same for reflection microscopes, where the specimen is illuminated from above through the objective lens and light reflected from the specimen is imaged by the objective.
The above-discussed limitation on the amount of light that can be transmitted through the objective lens also particularly limits the ability to observe fluorescence images through a microscope. This is so because, typically, high intensity light levels are needed to observe fluorescence images.
This limitation particularly affects the light intensity that can be obtained with fluorescence microscopes, where the specimen is illuminated through the objective lens. The illuminating light, typically called excitation light in fluorescence microscopy, is transmitted through the objective lens. This excitation light causes certain fluorescent molecules in the specimen to fluoresce. The light given off by this fluorescence is typically called emission light. The emission light is imaged through the objective lens. Thus, the intensity with which the specimen is observed varies as a function of the fourth power of the diameter of the lens.